The present invention relates to a self-pollinated genotype of Cymbopogon martinii christened as xe2x80x9cVaishnavixe2x80x9d and belonging to the family Gramineae. The plant xe2x80x9cVaishnavixe2x80x9d has been bred using the selfing system without causing inbreeding depression as against all existing palmarosa genotypes with almost no selfing but crossing system providing thereby a foundation for the long sought systematic plant breeding in palmarosa via deployment of scheme for introducing desirable gene(s) from diverse sources into xe2x80x9cVaishnavixe2x80x9d and fixing the introduced genes through simple selfings and progeny selections.
Essential oil bearing perennial grasses of India belong to the tribe Andropogoneae of which Cymbopogon forms an important genus comprising 140 species amongst which palmarosa (C. martinii) merits special importance being so far known as the major source of geraniol (C10H8O), an unsaturated primary terpene alcohol, the most widely used chemical in perfume industries. Although palmarosa, owing to its industrial importance, is grown world wide and has been given suitable emphasis for its genetic improvement, breeders"" efforts in the latter aspect have not as yet witnessed impressive success in developing high yielding varieties. Indeed, genetic improvement in palmarosa is very difficult primarily due to lack of scope for controlling its mating system. This is usually a cross-pollinated crop having very small tendency for setting seeds under selfing conditions. Further, very small size of florets in this crop greatly impedes manual emasculation and pollination. Thus, seed setting under controlled selfing and crossing based on testing are not feasible in palmarosa (Srivastava and Tyagi 1986; Patra and Sharma 1989; Patra et al. 1997; Patra and Kumar 1999). Although population improvement approach has repeatedly been resorted to earlier, not even a single variety till date is available, which would offer a guarantee for its sustained advancement in oil productivity as well as oil quality. Seed contamination from wild sources or, seed heterogeneity often caused by nonrandom mating among individuals within the population of a population cultivar leading to frequent deviations in oil productivity and quality are the general in features this out-breeding species. Keeping these limitations of the crop in view, planned efforts were made by the Applicants to explore the possibility of obtaining via extensive individual plant and half-sib family selections, a genotype with high oil yield potential and large tendency for seed setting or a half-sib genotype having much impressive oil yield potential coupled with ability to sustain homogeneity in its out-crossing population.
The main object of invention is to develop a novel palmarosa genotype via deployment of half-sib family selection with capacity to set large number of seeds under selfing conditions and having high oil yield potential.
Another object of invention is to ascertain the effect of high temperature of crop-burning practice for weed control, on the normal growth morphology, productivity and quality of the crop (palmarosa).
A further object of invention is to develop a novel palmarosa plant producing oil with high amount of geraniol. s
Half-sib family selections aimed at developing high yielding genotypes with high potential for setting seeds under selfing conditions were exercised in an old plant population the large part of which was got free of weeds and unwanted dry crop stubbles by deploying the xe2x80x9cburning techniquexe2x80x9d, generally applied to crops like palmarosa and sugarcane by the North Indian farmers. Flood irrigation was immediately given to the superficially burnt plants for the purpose of their survival and regeneration. Attempts were made to collect seeds from controlled selfings and open pollinations in burnt as well as unburned (normal) plants. None of the individuals in both cases of plants showed viable seeds under controlled selfing conditions. Viable seeds could be collected only from open pollinated plants. The absence of seed setting under selfing led to refer the open pollinated seeds of known mother plants as the xe2x80x9cseeds from natural half-sib matingxe2x80x9d. Seeds (half-sibs) of selected plants that are burnt and those that are not burnt were grown in a nursery and subsequently, the nursery seedlings were transplanted in blocks as half-sib families (S0 families). Seeds of the selected S0 plants were separated, collected and S1 populations were raised in the same way as done for S0 population. Whereas S0 plants of both types were normal looking with almost similar morphology, deviations in result in this regard were recorded in S1 generation (equivalent to F2 generation of normal plant crosses) for the burnt class of plants for three counts. First, among the 100, S1 half-sib families, 15 exhibited chlorophyll with frequency ranging between 0.6 to 7.8%. All the chlorophyll variants, with rare exceptions, were identical, all occurring in the form of xe2x80x9cZebra cutsxe2x80x9d as shown in FIG. 2A. None of the control (unburned half-sib) families reveal chlorophyll variation. Second, the burnt material in general, exhibited doubled somatic reproducibility in terms of tillering ability (30 to 70 tillers/plant against 15-20 Of the control). Third, the S1 family having maximum frequency of (7.8%) chlorophyll variants exhibited unique macro-variants with flower structure of self-pollinated plants like wheat and rice. This exceptional variant was multiplied by selfed seeds, characterized for its morpho-physiological plant attributes including oil content and productivity and was named as xe2x80x9cVaishnavixe2x80x9d. This unique genotype, despite its selfing, does not exhibit inbreeding depression. Vaishnavi, with all its plant-characters firmly fixed, highly excels all other existing genotypes for oil productivity. Inheritance study revealed that Vaishnavi is recessive homozygous for all its morphological traits which transmit all its traits en block from one generation to the next. Results of half-sib families of the burnt class of original plants and further experiment over the effect of superficial crop-burning temperature, convincingly raised the possibility that Vaishnavi as well as the chlorophyll variants derived their origins due to mutations induced in their progenitor (mother) plants by the high temperature of superficial crop-burning. Accordingly, high temperature from crop-burning has been suggested as a potent mutagen for inducing mutations in hardy grass crops like palmarosa.